Device and method at an exhaust afterteatment system for an engine

ABSTRACT

A method at an exhaust gas cleaning system for an engine ( 235 ) in which a reducing agent is added to a passage ( 290 ) for exhaust gases from the engine ( 235 ) for cleaning the exhaust gases. The exhaust gas cleaning system includes arrangements ( 270 ) that require a certain temperature level (Tmax) in order to achieve catalytic exhaust gas cleaning. The method is to distribute and store (s 430 ) a limited amount of reducing agent at temperature level (Tmax); and to use (s 440 ) during a cold start of the exhaust gas cleaning system, the distributed and stored reducing agent to achieve the catalytic exhaust gas cleaning. Also a computer program product ( 200; 210 ) to implement the method. Also an arrangement for an exhaust gas cleaning system for an engine ( 235 ), and a motor vehicle ( 100 ) equipped with the arrangement.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/889,538, filed Nov. 6, 2015, which is a 35 U.S.C. § 371national phase conversion of PCT/SE2014/050622, filed May 21, 2014,which claims priority of Swedish Patent Application No. 1350616-7, filedMay 21, 2013, the content of each of these applications are incorporatedby reference herein. The PCT International Application was published inthe English language.

TECHNICAL AREA

The present invention concerns a method for an exhaust gas cleaningsystem for an engine. The exhaust gas cleaning system may include an SCRcatalyst. The invention concerns also a computer program comprisingprogram code for a computer to implement a method according to theinvention. The invention concerns also an arrangement for an exhaust gascleaning system for an engine and a motor vehicle that is equipped withthe arrangement.

BACKGROUND

In currently available vehicles, urea, for example, a reductant is usedin SCR systems (where “SCR” is an abbreviation for “selective catalyticreduction”) comprising an SCR catalyst. The reductant and NO_(x) gas canreact in which the catalyst and be converted to nitrogen gas and water.Different types of reductants can be used in SCR systems. One commonlyused reductant is, for example, a reductant under the trademark, AdBlue.Such an SCR system may be applied also at a stationary application.

The SCR system may also include also a diesel oxidation catalyst (DOC).The DOC is arranged, among other things, to convert NO gas from anengine to NO₂ gas. In prior art technology, the DOC is arranged upstreamof the SCR catalyst and upstream also of the position for the dosage ofreduction agent, where relevant.

One type of SCR system includes a container that contains a reductant.The SCR system also has a pump configured to pump up the reductant fromthe container through a suction pipe and to supply it through apressurized pipe to a dosage unit that is arranged at an exhaust gassystem on the vehicle, for example, at an exhaust pipe at the exhaustgas system. The dosage unit is configured to inject a required amount ofreductant into an exhaust gas system upstream of the SCR catalystaccording to drive routines that are stored in a control unit in thevehicle.

There is an ever-present need to reduce the amount of emissions fromengines in motor vehicles. This applies to heavy motor vehicles such as,trucks and buses, since legal requirements for emissions arecontinuously being tightened.

During a “cold start” of an SCR system at the motor vehicle, it takes acertain period until the components that make up the system achieve anappropriate operating temperature. No reducing agent is dosed duringthis period, which means that it is then not possible to reduceundesired emissions to a suitable extent. Dosage during this period doesnot take place in order to avoid formation of deposits of reducing agentin the exhaust gas cleaning system upstream of the SCR catalyst. Incertain cases, it may be a period of up to 10 minutes, during which anengine creates emissions without reducing agent being dosed.

US20050069476 describes a system in which the dosage of reducing agentis carried out in association with switching off an engine of a vehicleto achieve the storage of ammonia in an SCR catalyst.

US20120023906 also describes a system in which the dosage of reducingagent is carried out in association with switching off an engine avehicle to achieve the storage of ammonia in an SCR catalyst.

These solutions, however, have a number of disadvantages. It isnecessary, for example, for an exhaust gas treatment system in this caseto demonstrate a rather high temperature in order for the reducing agentto be vaporized in an appropriate manner. Furthermore, the engine willneed to be operated, and in this case to produce a flow of exhaust gas,such that it is possible to add the dosed reducing agent to the SCRcatalyst. There is also an imminent risk with the prior art systems thatthat unreasonably large quantities of “urea deposits” are formed. Thesemay persist permanently or they may often increase in size if dosage iscontinuous, which will reduce the performance of the SCR system and maysometimes lead to a sound absorber, including the SCR catalyst, needingto be repaired or exchanged, with very high costs as a consequence.

SUMMARY OF THE INVENTION

One purpose of the present invention is to provide a new andadvantageous method for an exhaust gas cleaning system for an engine.

A further purpose of the invention is to provide a new and advantageousarrangement and a new and advantageous computer program for an exhaustgas cleaning system for an engine.

A further purpose of the invention is to provide a method, anarrangement and a computer program in order to achieve a reduction inthe amount of undesired emissions during a starting procedure of anengine, where a temperature at a post-processing system does not exceeda predetermined temperature, for example 200 degrees Celsius.

A further purpose of the invention is to provide a method, anarrangement and a computer program in order to achieve an increasedperformance at a platform that includes an engine with an exhaust gastreatment system.

A further purpose of the invention is to provide a method, anarrangement and a computer program in order to achieve an increasedperformance at an SCR system.

According to one aspect of the present invention, a method is providedfor an exhaust gas cleaning system for an engine which comprises addinga reducing agent to a passage for exhaust gases from the engine forcleaning the exhaust gases, wherein the exhaust gas cleaning systemincludes arrangements that require a certain temperature in order toachieve catalytic exhaust gas cleaning. The method includes thefollowing steps:

distributing and storing a limited amount of reducing agent in theexhaust gas passage upstream of the arrangements at a temperature thatdoes not exceed the certain temperature level; andduring a cold start of the exhaust gas cleaning system, using thedistributed and stored reducing agent in order to achieve the catalyticexhaust gas cleaning.

The limited amount of reducing agent is an appropriate amount

that is not included in an amount of reducing agent that is dosed duringcontinuous dosage, during normal, conventional or ordinary operation.The limited amount of reducing agent may be, for example, a deciliter ora half deciliter. The limited amount of reducing agent is intended to bestored temporarily for use during a cold start of the catalyticarrangements.

According to one aspect of the invention, ammonia (NH₃) may be releasedfrom the distributed and stored reducing agent at a temperature ofapproximately 130 degrees Celsius. That ammonia can advantageously beused at the catalytic arrangements before the ordinary dosage ofreducing agent is started. Ordinary dosage of reducing agent typicallystarts at a temperature of 180-200 degrees Celsius at the SCR catalyst.The distribution of reducing agent is an appropriately disperseddistribution. According to one design, the limited amount of reducingagent is distributed over as large a surface area at the exhaust gaspassage as possible. According to one design, the limited amount ofreducing agent is distributed over as large a surface area at avaporization module at the exhaust gas passage as possible.

According to the method according to the invention, there is anopportunity to distribute and store dosed reducing agent within a ratherwide range of temperatures with respect to the temperature at theexhaust gas treatment system, and in this case is not limited in themanner of certain prior art solutions, wherein storage of ammonia at thecatalyst must take place at temperatures of 200-350 degrees Celsius.

According to one design, the limited amount of reducing agent isdistributed and stored at a temperature at the exhaust gas treatmentsystem of 100-180 degrees Celsius. According to one design, the limitedamount of reducing agent is distributed and stored at a temperature atthe exhaust gas treatment system of 100-200 degrees Celsius. Accordingto one design, the limited amount of reducing agent is distributed andstored at a temperature at the exhaust gas treatment system of 120-160degrees Celsius. According to one design, the limited amount of reducingagent is distributed and stored at a temperature at the exhaust gastreatment system of 140 degrees Celsius.

The method may comprise the step of using the distributed and storedreducing agent through a crystalline condition of the reducing agent.This is an alternative method to increase the performance of an SCRsystem is achieved

The method may comprise the step of distributing and storing the limitedamount of reducing agent in association with switching off the engine.In this case, advantageous thermal energy of at least one of the exhaustgas passage and the vaporization module can be used according to oneaspect of the present invention. Distributing and storing the limitedamount of reducing agent, in association with switching off the engine,can produce lower ammonia slip than if the limited amount of reducingagent is distributed and stored in association with the start of theengine.

The method may comprise the step of distributing and storing the limitedamount of reducing agent in association with the start of the engine.

To distribute and store the limited amount of reducing agent afterswitching off the engine, as specified by one design of the presentinvention, means that the method can also be carried out if the SCRcatalyst is very hot, i.e. if the SCR catalyst has a temperature thatexceeds a certain limiting value, at the switching off the engine.

The method may comprise the step of distributing the limited amount ofreducing agent to form a reducing agent film in the exhaust gas passage.In this case, there is an advantageous possibility, during the heatingof an exhaust gas cleaning system, to convert and lead the distributedreducing agent to the catalytic arrangements at an early stage.

The method may comprise the step of distributing the limited amount ofreducing agent through the control of a reducing agent dosing unit. Thisprovides an accurate and efficient method according to the invention, inwhich a spray image of the reducing agent can be influenced in anappropriate manner.

The method may comprise the step of distributing the limited amount ofreducing agent through the control of a valve configuration at theexhaust gas treatment system. This achieves an accurate and efficientmethod according to the invention, in which a spray image of thereducing agent can be influenced in an appropriate manner.

The method may comprise the step of using an exhaust gas flow from theengine to achieve the distribution. This achieves a cost-effective andtime-efficient method according to the invention, in which distributionof the reducing agent can be influenced in an appropriate manner.

The method may comprise the step using pressurized air to achieve thedistribution. This achieves an efficient method according to theinvention, in which distribution of the reducing agent can be influencedin an appropriate manner.

The method is easy to implement in existing motor vehicles. Program codeat an exhaust gas cleaning system for an engine according to theinvention can be installed in a control unit of the vehicle duringmanufacture of the control unit. A purchaser of the vehicle can be giventhe opportunity of choosing the function of the method as an optionalextra. Alternatively, program code comprising program code to carry outthe innovative method at an exhaust gas cleaning system for an enginecan be installed in a control unit of the vehicle during upgrading at aservice station. The software in this case can be loaded into a memoryin the control unit.

Program code at an exhaust gas cleaning system for an engine can beupdated or exchanged where this is appropriate. Furthermore, differentparts of the program code at an exhaust gas cleaning system for anengine can be exchanged independently of each other. This modularconfiguration is advantageous from the point of view of maintenance.

According to one aspect of the present invention, a method is providedfor an exhaust gas cleaning system for an engine, comprising meansconfigured to dose a reducing agent to a passage for exhaust gases fromthe engine for the purposes of cleaning the exhaust gases, wherein theexhaust gas cleaning system includes arrangements that require a certaintemperature in order to achieve catalytic exhaust gas cleaning. Thearrangement also comprises means configured to distribute a limitedamount of reducing agent in the exhaust gas passage for its temporarystorage upstream of the arrangements at a temperature that does notexceed the certain temperature level in order to make possible, during acold start of the exhaust gas cleaning system, use of the distributedand stored reducing agent in order to achieve the catalytic exhaust gascleaning.

The distributed and stored reducing agent at the arrangement can be usedthrough a crystalline condition of the reducing agent.

The arrangement may comprise means configured to determine switching offof the engine, and means configured to distribute the limited amount ofreducing agent in the event that switching off the engine is determined.

The arrangement may comprise means configured to determine start of theengine, and means configured to distribute the limited amount ofreducing agent in the event that start of the engine is determined.

The arrangement may comprise means configured to distribute the limitedamount of reducing agent to form a reducing agent film in the exhaustgas passage.

The arrangement may comprise a reducing agent dosing unit arranged suchthat it can be controlled, configured to distribute the limited amountof reducing agent. The dosage unit may be assisted by pressurized air.In this case, a spray image of the dosed limited amount of reducingagent can be influenced in a desirable manner in order to achieve anappropriate distribution.

The arrangement may comprise a valve configuration that can becontrolled at the exhaust gas treatment system, and the valveconfiguration is configured to distribute the limited amount of reducingagent.

The arrangement may be configured to use an exhaust gas flow from theengine in order to achieve the distribution.

The arrangement may comprise pressurized air means configured to achievethe distribution.

The purposes described above are achieved also with a motor vehicle thatcomprises the arrangement at an exhaust gas cleaning system for anengine. The motor vehicle may be a lorry, a bus or a car.

According to one aspect of the invention, a computer program is providedat an exhaust gas cleaning system for an engine, where the computerprogram comprises program code in order to cause an electronic controlunit or a second computer connected to the electronic control unit tocarry out the steps according to the invention.

According to one aspect of the invention, a computer program is providedat an exhaust gas cleaning system for an engine, where the computerprogram comprises program code stored on a medium that can be read by acomputer in order to cause an electronic control unit or a secondcomputer connected to the electronic control unit to carry out the stepsaccording to the invention.

According to one aspect of the invention, a computer program productcomprising program code is provided stored on a medium that can be readby a computer, in order to carry out the method steps according to theinvention, where the program code is run on an electronic control unitor a second computer connected to the electronic control unit.

Further purposes, advantages and new distinctive features of the presentinvention will be made clear for one skilled in the arts by thefollowing details, as also during execution of the invention. While theinvention is described below, it should be obvious that the invention isnot limited to the specific details described. Those skilled in the artswill recognize further applications, modifications and executions withinother fields, which lie within the scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

For a more complete understanding of the present invention and furtherpurposes and advantages of it, reference is now made to the followingdetailed description, which is to be read together with the accompanyingdrawings in which the same reference numbers relate to the same parts inthe various drawings, and in which:

FIG. 1 illustrates schematically a vehicle, according to one embodimentof the invention;

FIG. 2 illustrates schematically an arrangement at an exhaust gascleaning system for an engine, according to one embodiment of theinvention;

FIG. 3 illustrates schematically a part of an exhaust gas cleaningsystem for an engine, according to one embodiment of the invention;

FIG. 4a illustrates schematically a flow diagram of a method accordingto one embodiment of the invention;

FIG. 4b illustrates schematically in greater detail a flow diagram of amethod according to one aspect of the invention; and

FIG. 5 illustrates schematically a computer according to one embodimentof the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a vehicle 100. The vehicle 100 taken as anexample consists of a drawing vehicle 110 and a trailer 112. The vehiclemay be a heavy vehicle, such as a lorry or a bus. Alternatively, thevehicle may be a car. The vehicle may be a truck.

It should be pointed out that the invention is suitable for applicationat a freely chosen suitable exhaust gas cleaning system that comprises acatalyst for catalytic exhaust gas cleaning. According to one design,the exhaust gas cleaning system includes an SCR catalyst. According toone design, the exhaust gas cleaning system includes an SCR system.According to one design, the exhaust gas cleaning system includes avaporization module that is arranged in an exhaust gas passage upstreamof a catalyst arrangement, for example including the SCR catalyst.According to one design, the exhaust gas cleaning system includes avaporization module that is arranged in an exhaust gas passage upstreamof arrangements for catalytic exhaust gas cleaning, for exampleincluding the SCR catalyst.

Aspects of the present invention are described herein with reference toan SCR system. One skilled in the arts will realize that the inventioncan be applied at other types of exhaust gas cleaning systems thanexhaust gas cleaning systems that include an SCR catalyst. In this case,a reducing agent that is suitable for the invention and that has thedesired properties is used.

It should be pointed out that the invention is suitable for applicationat an appropriate SCR system. The SCR system may comprise a DOC unit andan SCR catalyst and is therefore not limited to SCR systems at motorvehicles. The method according to the invention and the arrangementaccording to the invention are, according to one aspect of theinvention, well-suited to other platforms than motor vehicles thatinclude an exhaust gas cleaning system, for example, water-goingvessels. The water-going vessels may be of any chosen type such as motorboats, vessels, ferries or ships.

The method according to the invention and the arrangement according tothe invention are, according to one aspect of the invention, well-suitedfor use also with, for example, systems that include, for example, arock crusher or similar.

The method according to the invention and the arrangement according tothe invention are, according to one aspect of the invention, well-suitedfor use also with, for example, systems that include at least one ofindustrial engines and motor-driven industrial robots.

The method according to the invention and the arrangement according tothe invention are, according to one aspect of the invention, well-suitedfor use also with, for example, various types of power station, such as,electrical power stations that comprise a diesel-powered electricalgenerator.

The method according to the invention and the arrangement according tothe invention are well-suited for a freely chosen suitable engine systemthat includes an engine, an SCR system and an SCR catalyst, such as, arailway engine or another platform.

The method according to the invention and the arrangement according tothe invention are well-suited for a suitable system that includes anNO_(x) generator and an SCR system that includes a vaporization moduleand an SCR catalyst.

The method according to the invention and the arrangement according tothe invention are well-suited for a system that includes what is knownas a “cDPF” unit. The method according to the invention and thearrangement according to the invention are well-suited for a system thatincludes what is known as an “ASC” unit.

In this document, the term “link” refers to a communication link thatmay be a physical line, such as an opto-electronic communication line,or a non-physical line, such as a wireless connection, for example aradio link or microwave link.

In this document, the term “line” refers to a passage to contain and totransport a fluid, such as, a reductant in fluid form. The line may be apipe of freely chosen dimension. The line may be of a freely chosen andsuitable material, such as, plastic, rubber or metal.

In this document, the terms “reductant” and “reducing agent” refer to anagent that is used to react with certain emissions in an SCR system.These emissions may be, for example, NO_(x) gas. The terms “reductant”and “reducing agent” are used synonymously in this document. Thereductant according to one embodiment is known as AdBlue. Naturally,other types of reductants can be used. AdBlue is given as an example ofa reductant in this document, but one skilled in the arts will realizethat the innovative method and the innovative arrangement can be broughtto reality for other types of reductants.

The reducing agent may consist of an aqueous solution including urea.The reducing agent may include an appropriate concentration of urea. Thereducing agent may be in liquid form when dosed. The reducing agent maybe in gaseous form when dosed. The reducing agent may be in solid formwhen dosed.

FIG. 2 shows an arrangement 299 at the vehicle 100. The arrangement 299may be arranged in the drawing or towing vehicle 110. The arrangement299 may constitute a part of an SCR system or it may include an SCRsystem. An engine 235 suitable for the invention is illustratedschematically in FIG. 2. The engine 235 is a combustion engine. Theengine 235 may be a diesel engine. Alternatively, the engine 235 may bedriven by petrol, gas or ethanol. An exhaust gas passage 290 is arrangedto lead exhaust gases from the engine 235 to its surroundings. Theexhaust gas passage 290 may be included in a sound absorber unit.

The arrangement 299 comprises a first control unit 200 configured tocontrol operation of the engine 235.

The arrangement 299 of this example comprises a container 205 configuredto contain a reductant. The container 205 is configured to contain asuitable amount of reductant and to be filled when necessary.

A first line 271 is arranged to lead the reductant to a pump 230 fromthe container 205. The pump 230 may be a freely chosen suitable pump.The pump 230 may be a membrane pump comprising at least one filter. Thepump 230 may be driven by means of an electric motor (not shown in thedrawings). The pump 230 is configured to pump the reductant up from thecontainer 205 through the first line 271 and to supply the reductantthrough a second line 272 to a dosage unit 250. The dosage unit 250 mayinclude an electrically controlled dosage arrangement, to control a flowof reductant that has been supplied to the exhaust gas system can becontrolled. The first control unit 200 is arranged for communicationwith the dosage unit 250 over a link L250. The pump 230 is configured toplace the reductant under pressure in the second line 272. The dosageunit 250 is arranged with a throttle unit, which can be referred to as athrottle valve, against which the pressure at the reductant can be builtup in the arrangement 299.

The dosage unit 250 is to supply the reductant to the exhaust gaspassage 290 at the vehicle 100. To be more precise, the dosage unit 250is arranged to supply, in a controlled manner, a suitable amount ofreductant to the exhaust gas passage 290 at the vehicle 100, accordingto one aspect of the method according to the invention. According tothis method, an SCR catalyst 270 is arranged downstream of a position atthe exhaust gas system at which supply of reductant takes place. Theamount of reductant that is supplied into the exhaust gas system isintended to be used in the SCR catalyst in order to reduce the amount ofundesired emissions.

According to an example, a diesel oxidation catalyst 259 is arranged inthe exhaust gas passage 290 downstream of the engine. The dieseloxidation catalyst 259 is arranged in the exhaust gas passage 290upstream of the SCR catalyst 270 and upstream of the dosage unit 250.The diesel oxidation catalyst 259 may be known as a “DOC unit”. Thediesel oxidation catalyst 259 is arranged to convert NO gas from theengine 235 to NO₂ gas. The diesel oxidation catalyst 259 may be arrangedalso to oxidise fuel in order to achieve a temperature increase at theexhaust gases.

The exhaust gas passage 290 comprises a vaporization module 269. Theexhaust gas passage 290 may include a piece of pipe upstream of thevaporization module 269. The vaporization module 269 is arrangedupstream of the SCR catalyst 270. The vaporization module 269 isarranged downstream of the dosage unit 250. The vaporization module 269may be designed in an appropriate manner. The vaporization module 269 isarranged to make possible efficient vaporization of dosed reducingagent. According to one aspect of the present invention, thevaporization module 269 is arranged to store a limited amount ofreducing agent that has been added, which can be used for exhaust gascleaning during a cold start of the SCR system. According to one aspectof the present invention, the exhaust gas passage 290 is arranged tostore a limited amount of reducing agent that has been added, which canbe used for exhaust gas cleaning during a cold start of the SCR system.The added limited amount of reducing agent can be stored in the exhaustgas passage 290 upstream of the vaporization module 269 or in thevaporization module 269.

The dosage unit 250 is arranged at the exhaust gas passage 290 that isarranged to lead exhaust gases from the engine 235 at the vehicle 100 tothe DOC unit 259, onwards to the vaporization module 269 and the SCRcatalyst 270, and onwards to the surroundings of the vehicle.

A third line 273 is arranged between the dosage unit 250 and thecontainer 205. The third line 273 is configured to lead back a certainamount of the reductant that has been fed to the dosage valve 250 to thecontainer 205.

The first control unit 200 is configured for communication with the pump230 through a link L230. The first control unit 200 is configured tocontrol operation of the pump 230. According to one example, the firstcontrol unit 200 is configured to control the pump 230 by means of anelectric motor (not shown in the drawings). The first control unit 200is arranged to influence a working pressure in the second line 272. Thiscan take place in various suitable ways. According to one example, thefirst control unit 200 is configured to change a prevalent rate ofrevolution, RPM, at the pump 230. The pressure can in this case bechanged in the manner desired. The working pressure can be increased byincreasing the rate of revolution at the pump 230. The working pressurecan be decreased by decreasing the rate of revolution at the pump 230.By controlling the pressure of the reducing agent in the second line 272by means of the pump 230, a spray pattern of the dosed reducing agentcan be influenced and in this way controlled. In this way, adistribution of the dosed reducing agent in the exhaust gas passage 290can be controlled in an appropriate manner. In particular, a spraypattern of the dosed reducing agent in a limited amount, according toone aspect of the present invention, can be controlled such that adesired distribution and storage of the reducing agent is achieved.

By controlling the pressure of the reducing agent in the second line 272by means of the throttle unit at the dosage unit 250, a spray pattern ofthe dosed reducing agent can be influenced and in this way controlled.In this way, a distribution of the dosed reducing agent in the exhaustgas passage 290 can be controlled in an appropriate manner.

According to one design, the dosage unit 250 is arranged with a nozzlethat can be controlled. The first control unit 200 is arranged tocontrol the nozzle. In this way, the nozzle can be directed in anappropriate manner. In this way, a spray pattern of the dosed reducingagent can be influenced and in this way controlled. In this way, adistribution of the dosed reducing agent in the exhaust gas passage 290can be controlled in an appropriate manner.

The first control unit 200 is arranged for communication with a firsttemperature sensor 240 through a link L240. The temperature sensor 240is arranged to detect a prevalent temperature T1 of a flow of exhaustgases from the engine of the vehicle. According to one example, thefirst temperature sensor 240 is arranged at the exhaust gas passage 290immediately downstream of the engine of the vehicle and upstream of theDOC unit, and in this way upstream of the dosage unit 250. The firsttemperature sensor 240 may be arranged at a suitable location at theexhaust gas passage 290. The first temperature sensor 240 is arranged todetect continuously a prevalent temperature T1 of the flow of exhaustgases and to send signals containing information about the prevalenttemperature T1 over the link L240 to the first control unit 200.

The first control unit 200 is arranged for communication with a secondtemperature sensor 260 through a link L260. The second temperaturesensor 260 may be arranged to detect a prevalent temperature T2 at asurface in the exhaust gas system at which the reducing agent isvaporized. The second temperature sensor 260 may be arranged to detect aprevalent temperature T2 at the exhaust gas passage 290 at a suitablelocation. The second temperature sensor 260 may be arranged to detect aprevalent temperature T2 at a suitable surface or component of theexhaust gas passage 290.

According to one example, the second temperature sensor 260 is arrangedat the exhaust gas passage 290 upstream of the dosage unit 250.According to one example, the second temperature sensor 260 is arrangedto detect a prevalent temperature T2 at the DOC unit 259. According toone example, the second temperature sensor 260 is arranged in theexhaust gas passage 290 upstream of the dosage unit 250. According to asecond example, the second temperature sensor 260 is arranged in thevaporization module 269 or in the SCR catalyst 270 downstream of thedosage unit 250. The second temperature sensor 260 is arranged to detectcontinuously a prevalent temperature T2 of a surface or a component atthe exhaust gas passage 290 and to send signals containing informationabout the prevalent temperature T2 over the link L260 to the firstcontrol unit 200.

According to one design, at least one of the first control unit 200 andthe second control unit 210 is arranged to calculate the firsttemperature T1. This can take place by means of a stored calculationmodel. At least one of the first control unit 200 and the second controlunit 210 may be arranged to calculate the first temperature T1 on thebasis of, for example, a prevalent mass flow of exhaust gases, theprevalent rate of revolution of the engine, and the prevalent load onthe engine.

According to one design, at least one of the first control unit 200 anda second control unit 210 is arranged to calculate the secondtemperature T2. This can take place by means of a stored calculationmodel. At least one of the first control unit 200 and the second controlunit 210 may be arranged to calculate the second temperature T2 on thebasis of, for example, an ambient temperature determined at the vehicle100. At least one of the first control unit 200 and the second controlunit 210 may be arranged to calculate the second temperature T2 on thebasis of, for example, at least one of a determined period of time sincethe engine 235 was switched of, the ambient temperature at the vehicle100, the determined accumulated heat production at the engine 235 beforeswitching off, and the temperature at the engine 235 when it wasswitched off. At least one of the first control unit 200 and the secondcontrol unit 210 may be arranged to calculate the second temperature T2on the basis of the first temperature T1.

The first control unit 200 is arranged to dose, by means of the dosageunit 250 that is arranged such that it can be controlled, and in thisway distribute and store a limited amount of reducing agent in theexhaust gas passage 290 upstream of the SCR catalyst 270 at atemperature that does not exceed a predetermined temperature, forexample 190 degrees Celsius. This distributed and stored limited amountof reducing agent can, during a cold start of an exhaust gas cleaningsystem including the vaporization module 269 and SCR catalyst 270, beused for the purpose of cleaning exhaust gases.

The first control unit 200 is arranged to dose, by means of the dosageunit 250, the reducing agent such that the reducing agent, according toone aspect of the invention, can be used of the purpose of cleaningexhaust gases after first having been in a solid state, i.e. in acrystalline condition, and subsequently converted to gaseous form foruse at the SCR catalyst 270. The reducing agent in gaseous form mayinclude ammonia.

The first control unit 200 may be arranged to dose, by means of thedosage unit 250, and in this way to distribute and store, the limitedamount of reducing agent in association with switching off of the engine235. The first control unit 200 may be arranged to dose, by means of thedosage unit 250, and in this way to distribute and store, the limitedamount of reducing agent in association with start of the engine 235.The first control unit 200 may be arranged to distribute, by means ofthe dosage unit 250, the limited amount of reducing agent in order toform at least one film of reducing agent in at least one of the exhaustgas passage 290 and the vaporization module 269. The first control unit200 may be arranged to control the dosage unit 250 in order to dose,according to one aspect of the invention, the limited amount of reducingagent such that a suitable layer of reducing agent according to theinvention is formed in at least one of the exhaust gas passage 290 andthe vaporization module 269. The first control unit 200 may be arrangedto control a valve configuration at the SCR system in order to achievean appropriate working pressure of the reducing agent, whereby anappropriate distribution of the limited amount of reducing agent isachieved at the exhaust gas treatment system. The first control unit 200may be arranged to dose and in this way distribute and store the limitedamount of reducing agent through the use, during the switching off ofengine 235, of an exhaust gas flow from the engine 235 in order toachieve the distribution. The first control unit 200 may be arranged tocontrol, during the distribution and storage, pressurized air means inorder to achieve a suitable layer of reducing agent, according to theinvention, in at least one of the exhaust gas passage 290 and thevaporization module 269.

The first control unit 200 is arranged for communication with the dosageunit 250 over a link L250. The first control unit 200 is arranged tocontrol operation of the dosage unit 250 in order, for example, toregulate the supply of the reductant to the exhaust gas system of thevehicle 100.

The first control unit 200 may be arranged to calculate a mass flow MFof exhaust gases from the engine of the vehicle. The first control unit200 may be arranged to determine continuously a mass flow MF of exhaustgases from the engine of the vehicle. This may take place in a suitablemanner. The first control unit 200 may be arranged, according to oneexample, to distribute, by means of the dosage unit 250, the limitedamount of reducing agent at the exhaust gas passage 290 on the basis ofthe exhaust gas mass flow MF that has been determined. The exhaust gasflow during the switching off of the engine 235 can be used to achievean appropriate distribution of the dosed limited amount of reducingagent in at least one of the exhaust gas passage and the vaporizationmodule 269. According to the method according to the invention, thepurpose is not to store reducing agent in the form of, for example,ammonia in the SCR catalyst 270.

According to one design, the subsystem comprises a mass flow sensor (notshown in the drawings) that is arranged to measure continuously aprevalent mass flow MF of exhaust gases from the engine of the vehicle100 in the exhaust gas passage 290 upstream of the SCR catalyst 270. Themass flow sensor is arranged to send continuously signals comprisinginformation about a prevalent mass flow MF of exhaust gases to the firstcontrol unit 200 over a link arranged for this purpose.

The second control unit 210 is arranged for communication with the firstcontrol unit 200 over a link L210. The second control unit 210 may beconnected to the first control unit 200 in a manner that allows it to beremoved. The second control unit 210 may be a control unit that isexternal to the vehicle 100. The second control unit 210 may be arrangedto carry out the method steps according to the invention. The secondcontrol unit 210 may be used to transfer program code to the firstcontrol unit 200, in particular, program code to carry out the methodaccording to the invention. Alternatively, the second control unit 210may be arranged for communication with the first control unit 200 overan internal network in the vehicle. The second control unit 210 may bearranged to carry out essentially similar functions as the first controlunit 200, such as, to supply and in this way distribute and store alimited amount of reducing agent in the exhaust gas passage 290 upstreamof the SCR catalyst 270 at a temperature that does not exceed thecertain temperature level Tmax, and to use, during a cold start of theexhaust gas cleaning system, the distributed and stored reducing agentin order to achieve the catalytic exhaust gas cleaning.

According to one design, more than one dosage unit 250 can be provided.The first control unit 200 is in this case arranged to control thesefurther dosage units in a corresponding manner as the dosage unit 250.In the case in which more than one dosage unit 250 is used according tothe method according to the invention, these may interact in order toachieve an essentially optimal distribution and storage of the limitedamount of reducing agent added. The first control unit 200 is arrangedto control the various dosage units such that dosage of the limitedamount of reducing agent takes place sequentially, alternately orsimultaneously, or in a combination of these methods. The total amountof the limited amount of reducing agent that is to be distributed andstored according to the present invention may be distributed between thevarious dosage units in an appropriate manner. According to one designgiven as an example, in which the arrangement 299 includes two dosageunits 250, the relevant dosage units 250 may each dose half of thelimited amount of reducing agent. According to one design given as anexample, in which the arrangement 299 includes two dosage units 250, therelevant dosage units 250 may dose 90% and 10%, respectively, of thelimited amount of reducing agent.

According to one embodiment, pressurized air means 289 is provided. Thefirst control unit 200 is in this case arranged for communication withthe pressurized air means 289 through a link L289. The first controlunit 200 is arranged to control the pressurized air means 289. Thepressurized air means 289 is configured to supply a flow of air at theexhaust gas passage 290 in order to achieve an appropriate distributionand storage of the limited amount of reducing agent at at least one ofthe exhaust gas passage 290 and the vaporization module 269. Thepressurized air means is described with reference also to FIG. 3. Thepressurized air means 289 can be advantageously used for thedistribution of the limited amount of reducing agent when the engine 235is switched off. The pressurized air means 289 can be advantageouslyused for the distribution of the limited amount of reducing agent whenthe reducing agent is dosed according to the present invention.

FIG. 3 illustrates schematically a part of an exhaust gas cleaningsystem for an engine 235, according to one embodiment of the invention.

In this case, the exhaust gas passage 290 including the vaporizationmodule 269 and the SCR catalyst 270 are illustrated. Furthermore, thedosage unit 250, the second line 272 and the third line 273 areillustrated. The pressurized air means 289 is arranged to supply, on thebasis of control signals received through the link L289 from the firstcontrol unit 200, pressurized air to the exhaust gas passage 290 in anappropriate manner. A suitable distribution of the limited amount ofreducing agent can in this way be achieved according to one aspect ofthe present invention. It should be noted that the pressurized air meansmay be arranged, as an alternative, to supply a freely chosen suitablegas to the exhaust gas passage 290, not necessarily air.

According to one aspect of the present invention, a limited amount ofreducing agent is dosed, and in this manner distributed and stored, at atemperature at the exhaust gas passage 290 that does not exceed apredetermined temperature Tmax. The distributed reducing agentconstitutes in this way one or several thin films F at the walls at theexhaust gas passage 290 or in the vaporization module 269. The film Fcan also be denoted by layer/coat/lining. The film F can, according toone design, be thinner than 1 mm, for example 0.1 mm or 0.5 mm. The filmF can, according to one design, be thicker than 1 mm. The film F cancomprise sections at which there is no reducing agent present. The filmF can, therefore, comprise one or several holes. The film F isadvantageously distributed in such a manner that reducing agent can berapidly emitted on increases in temperature during the cold start of theSCR system. The reducing agent can in this way be led, in an appropriatecomposition (for example, ammonia) to the SCR catalyst 270 for exhaustgas cleaning.

The film F can be constituted, at least partially, by reducing agent inthe fluid phase. The film F can be constituted, at least partially, byreducing agent in the solid phase, for example in the form of crystalsof reducing agent.

According to one design given as an example, distribution means 333 maybe provided. These distribution means 333 may be designed in a suitablemanner, as, for example, a net or propeller. The distribution means 333are arranged to distribute the limited amount of reducing agent in anappropriate manner. In this way, an efficient means is obtained tooptimize the distribution of the limited amount of reducing agent in atleast one of the exhaust gas passage 290 and the vaporization module269. The distribution means 333 are arranged downstream of the dosageunit 250. The distribution means 333 are arranged to finely disperse andspread the dosed limited amount of reducing agent during thedistribution and storage of the same in at least one of the exhaust gaspassage 290 and the vaporization module 269.

FIG. 4a illustrates schematically a flow diagram of a method at anexhaust gas cleaning system for an engine 235 in which a reducing agentis added to a passage 290 for exhaust gases from the engine 235 for thepurposes of cleaning the exhaust gases, and where the exhaust gascleaning system includes arrangements 270 that require a certaintemperature level Tmax in order to achieve catalytic exhaust gascleaning. The method comprises a first method step s401. The step s401comprises the following steps:

-   -   to distribute and store a limited amount of reducing agent in        the exhaust gas passage 290 upstream of the arrangements 270 at        a temperature that does not exceed the certain temperature level        Tmax, and    -   to use during a cold start of the exhaust gas cleaning system        the distributed and stored reducing agent in order to achieve        the catalytic exhaust gas cleaning.

The method is terminated after the step s401.

FIG. 4b illustrates schematically a flow diagram of a method at anexhaust gas cleaning system for an engine 235 in which a reducing agentis added to a passage 290 for exhaust gases from the engine 235 for thepurposes of cleaning the exhaust gases, and where the exhaust gascleaning system includes arrangements 270 that require a certaintemperature level Tmax in order to achieve catalytic exhaust gascleaning, according to one aspect of the present invention.

The method includes a first method step s410. The method step s410includes the step to determine a currently prevalent second temperatureT2 at the exhaust gas passage 290. This may involve determining a secondtemperature T2 at, for example, the DOC unit 259, the SCR catalyst 270,the vaporization module 269 or a wall at the exhaust gas passage 290.The method may include the step of determining the first temperature T1.The second temperature T2 can be determined on the basis of the firsttemperature T1 of the exhaust gases from the engine 235. In the case inwhich the second temperature T2 does not exceed a predeterminedtemperature Tmax, for example 180 or 200 degrees Celsius, the methodaccording to the invention can be carried out. After the method steps410, a subsequent method step s420 is in this case carried out.

The method step s420 includes the step of determining a distribution ofa limited amount of reducing agent. The step s420 can include the stepof determining an amount or volume of reducing agent that is tocorrespond to the limited amount of reducing agent. The volume may be,according to one example, 0.1 liter, or 0.05 liter. The limited amountof reducing agent is an appropriate amount of reducing agent. Thelimited amount of reducing agent may be, for example, 30, 100 or 600gram of Adblue. The distribution of the limited amount of reducing agentis adapted, according to the method according to the invention, suchthat it does not lead to excessively large crystals of reductant beingformed in the exhaust gas passage 290 or in the vaporization module 269.The limited amount of reducing agent may be an amount based on orrelated to, or both based on and related to, a maximum possible storageof ammonia in an SCR catalyst. An SCR catalyst may have a certainmaximum possible storage capacity (the amount of ammonia that the SCRcatalyst can “hold” at a certain temperature) that is x gram per unit ofvolume, for example x gram of ammonia per liter. The maximum possiblestorage in this way thus depends on the magnitude/volume of the SCRcatalyst specified in the units of “liters”. The maximum possiblestorage at the SCR catalyst may depend also on, and it may be specifiedin, some other applicable unit. The maximum possible storage of ammoniain an SCR catalyst may be 0.5 gram/liter. The maximum possible storageof ammonia in an SCR catalyst may be 0.8 gram/liter. The maximumpossible storage of ammonia in an SCR catalyst may be 2 gram/liter. Aswill be realized, the maximum possible storage of ammonia may be lessthan 0.5 gram/liter or greater than 2 gram/liter. The limited amount ofreducing agent may be an amount of the same order of magnitude as amaximum possible storage of ammonia in an SCR catalyst. The limitedamount of reducing agent may be an amount that is less than, or equalto, a maximum possible storage of ammonia in the SCR catalyst. Thelimited amount of reducing agent may be an amount that is greater than,or equal to, a maximum possible storage of ammonia in the SCR catalyst.The limited amount of reducing agent may be an amount that is less than,or equal to, 50% of a maximum possible storage of ammonia in the SCRcatalyst. The limited amount of reducing agent may be an amount that isless than, or equal to, 25% of a maximum possible storage of ammonia inthe SCR catalyst. The limited amount of reducing agent may be an amountthat corresponds to or results in 50 gram of ammonia that reacts withNO_(x) gas in the SCR catalyst. The limited amount of reducing agent maybe an amount that corresponds to or results in 25 gram of ammonia thatreacts with NO_(x) gas in the SCR catalyst. The limited amount ofreducing agent may be an amount that corresponds to or results in 8 gramof ammonia that reacts with NO_(x) gas in the SCR catalyst. The limitedamount of reducing agent may be an amount that corresponds to or resultsin 2.5 gram of ammonia that reacts with NO_(x) gas in the SCR catalyst.The limited amount of reducing agent may be an amount that results inammonia slip during a subsequent increase in temperature from the SCRcatalyst that does not exceed a predetermined limiting value. Thelimited amount of reducing agent may be an amount that results in anammonia slip during a subsequent increase in temperature from the SCRcatalyst that, after having passed an ASC (ammonia slip catalyst), doesnot exceed a predetermined limiting value. The limiting value may beessentially equal to zero. The limiting value may be a suitablepredetermined value. The limiting value may be a suitable predeterminedvalue that is based on currently valid legal requirements. The resultingammonia slip may be an estimated or predicted resulting ammonia slip.The resulting ammonia slip may be estimated/predicted/calculated throughthe use of an applicable calculation model. The limited amount ofreducing agent may be an amount that corresponds to or results in thatan amount of crystals of reducing agent that are formed in the exhaustgas passage 290 or in the vaporization module 269 does not exceed apredetermined maximum amount of reducing agent. The amount of reducingagent crystals may correspond to the above-mentioned amount of ammoniathat reacts with NO_(x) gas in the SCR catalyst. The limited amount ofreducing agent may be an amount that is based on properties, such as forexample possible storage capacity, of the SCR catalyst during a coldstart. The limited amount of reducing agent may be an amount that isbased on properties of the SCR catalyst during a process that follows acold start.

The limited amount of reducing agent is to be distributed and stored,according to one aspect of the invention, only temporarily in theexhaust gas passage 290 before its use during a cold start of the SCRsystem, i.e. the limited amount of reducing agent is not to bepermanently stored in the exhaust gas passage 290. The temporarilystored limited amount of reducing agent is to be consumed according tothe method according to the invention. The temporarily stored limitedamount of reducing agent/ammonia is intended to react with NO_(x) gas inthe SCR catalyst and to be converted to nitrogen and water.

The step s420 includes also the step of determining an appropriatemanner to distribute the limited amount of reducing agent after dosage.A permanent configuration for the dosage can in this way be determined.The permanent configuration may, for example, concern a period of timeduring which the dosage unit is open and during which the dosing ofreducing agent takes place. It can in this way be determined whether thepressurized air means 289 is to be used for the distribution. It can inthis way be determined whether a flow of exhaust gases from the engine235 is to be used for the distribution. It can in this way be determinedwhether more than one dosage unit 250 is to be used. It can in this waybe determined how a suitable spray image for the dosage is to bedesigned. After the method step s420, a subsequent method step s430 iscarried out.

The method step s430 includes the step of distributing and storing thelimited amount of reducing agent in the appropriate manner that has beendetermined. This may be carried out in various suitable ways. After themethod step s430, a subsequent method step s440 is carried out.

The method step s440 includes the step of using the limited amount ofdistributed and stored reducing agent for exhaust gas cleaning in theSCR catalyst 270. As the second temperature T2 gradually increasesduring heating of the SCR system, the stored reducing agent willgradually be emitted in the form of, for example, ammonia and can be ledby means of the exhaust gas flow of the engine to the SCR catalyst 270.According to one alternative design, the stored reducing agent can begradually emitted in the form of, for example, gaseous ammonia and canbe led by means of a flow of air caused by the pressurized air means tothe SCR catalyst 270, possibly in combination with the exhaust gas flowfrom the engine 235. According to the invention, the complete limitedamount of distributed and stored reducing agent that has temporarilybeen present in at least one of the exhaust gas passage 290 and thevaporization module 269 is used. The method according to the inventionis ended after the method step s440.

With reference to FIG. 5, there is shown a drawing of a design of anarrangement 500. The control units 200 and 210 that are described withreference to FIG. 2 may, in one design, comprise the arrangement 500.The arrangement 500 comprises a non-transient memory 520, a dataprocessing unit 510 and a read/write memory 550. The non-transientmemory 520 has a first section of memory 530 in which a computerprogram, such as an operating system, is stored in order to control thefunction of the arrangement 500. Furthermore, the arrangement 500comprises a bus controller, a serial communication port, I/O means, anND converter, a unit for the input and transfer of time and date, anevent counter and an interrupt controller (not shown in the drawing).The non-transient memory 520 has also a second section of memory 540.

A computer program P is provided that comprises procedures at an exhaustgas cleaning system for an engine 235 in which a reducing agent is addedto a passage 290 for exhaust gases from the engine 235 for the purposesof cleaning the exhaust gases, and where the exhaust gas cleaning systemincludes arrangements 270 that require a certain temperature level Tmaxin order to achieve catalytic exhaust gas cleaning.

The computer program P may comprise procedures to dose a limited amountof reducing agent and in this way to distribute and store the limitedamount of reducing agent in at least one of the exhaust gas passage 290and in a vaporization module arranged upstream of the exhaust gaspassage upstream of the SCR catalyst 270 at a temperature that does notexceed the certain temperature level Tmax, in order to provide and touse, during a cold start of the exhaust gas cleaning system, thedistributed and stored reducing agent in order to achieve the catalyticexhaust gas cleaning. The computer program P may comprise procedures todistribute and store the limited amount of reducing agent in associationwith switching off of the engine 235. The computer program P maycomprise procedures to distribute and store the limited amount ofreducing agent in association with start of the engine 235. The computerprogram P may comprise procedures to distribute the limited amount ofreducing agent in order to form a reducing agent film F in at least oneof the exhaust gas passage 290 and the vaporization module 269. Thecomputer program P may comprise procedures to distribute the limitedamount of reducing agent through the control of a reducing agent dosingunit 250. The computer program P may comprise procedures to distributethe limited amount of reducing agent through the control of a valveconfiguration (not shown in the drawings) at the exhaust gas treatmentsystem. The computer program P may comprise procedures to control theoperation of the engine 235 and in this way to use an exhaust gas flowfrom the engine 235 in order to achieve the distribution. The computerprogram P may comprise procedures to control pressurized air means 289and in this way to use pressurized air supplied in the exhaust gaspassage 290 in order to achieve the distribution.

The program P may be stored in an executable form or in a compressedform in at least one of a memory 560 and a read/write memory 550.

When it is described that the data processing unit 510 carries out acertain function, it is to be understood that the data processing unit510 carries out a certain part of the program that is stored in thememory 560, or a certain part of the program that is stored in theread/write memory 550.

The data processing arrangement 510 can communicate with a data port 599through a data bus 515. The non-transient memory 520 is intended forcommunication with the data processing unit 510 through a data bus 512.The separate memory 560 is intended to communicate with the dataprocessing unit 510 through a data bus 511. The read/write memory 550 isarranged to communicate with the data processing unit 510 through a databus 514. The links L210, L230, L240, L250, L260 and L289 can, forexample, be connected to the data port 599 (see FIGS. 2 and 3).

When data is received at the data port 599, it is temporarily stored inthe second section of memory 540. When the data that has been receivedhas been temporarily stored, the data processing unit 510 is preparedfor the execution of code in a manner that has been described above.

According to one design, signals received at the data port 599 compriseinformation about a prevalent temperature T2 at a suitable surface at,or a component in, the exhaust gas passage 290, for example at least oneof a temperature T2 prevalent at the SCR catalyst 270 and a temperatureT2 at the DOC unit 259.

The signals that are received at the data port 599 can be used by thearrangement 500 to dose and in this way to distribute and store alimited amount of reducing agent in the exhaust gas passage upstream ofthe SCR catalyst at a temperature that does not exceed the certaintemperature level Tmax. The distributed and stored reducing agent can inthis way be used during a cold start of the exhaust gas cleaning system.

Parts of the methods described here may be carried out by thearrangement 500 with the aid of the data processing unit 510, which runsthe program stored in the memory 560 or in the read/write memory 550.When the arrangement 500 runs the program, the method described here isexecuted.

The previous description of the preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription of the invention. It is not intended to be exhaustive or tolimit the invention to the variants that have been described. Manymodifications and variations will be obvious for one skilled in thearts. The embodiments were selected and described in order to bestexplain the principles of the invention and its practical applications,and thus to make it possible for those skilled in the arts to understandthe invention for various embodiments and with the various modificationsthat are appropriate for the intended use.

What is claimed is:
 1. A method for operating an exhaust gas cleaningsystem of a combustion engine, the system comprising: an exhaust passagefor leading exhaust gases from the engine to arrangements that require aselected temperature level (Tmax) in order to achieve catalytic exhaustgas cleaning, the arrangements including an SCR catalyst, and the methodcomprising the steps: distributing and storing a limited amount ofreducing agent in a vaporization module upstream of the SCR catalyst;and during the cold start of the exhaust gas cleaning system, using thedistributed and stored reducing agent to achieve the catalytic exhaustgas cleaning.
 2. The method according to claim 1, further comprising thestep: using the distributed and stored reducing agent through acrystalline condition of the reducing agent.
 3. The method according toclaim 1, further comprising the step: distributing and storing thelimited amount of reducing agent in association with switching off theengine.
 4. The method according to claim 1, further comprising the stepof: distributing and storing the limited amount of reducing agent inassociation with start of the engine.
 5. The method according to claim1, further comprising the step of: distributing a limited amount ofreducing agent to form a reducing agent film at the wall of the exhaustgas passage.
 6. The method according to claim 1, further comprising thestep of: distributing the limited amount of reducing agent through thecontrol of a reducing agent dosing unit.
 7. The method according toclaim 1, further comprising the step of: distributing the limited amountof reducing agent through the control of a valve configuration at theexhaust gas treatment system.
 8. The method according to claim 1,further comprising the step of: using an exhaust gas flow from theengine for achieving the distribution.
 9. A computer program productcomprising a non-volatile computer readable storage medium, and acomputer program comprising program code stored on the medium readableby a computer or an electronic control unit; and the program code isconfigured to carry out the method steps according to claim 1, when theprogram code is run on an electronic control unit or a second computerconnected to the electronic control unit.